Characterization of adenosine receptors in bovine chondrocytes and fibroblast-like synoviocytes exposed to low frequency low energy pulsed electromagnetic fields.

摘要

Objective: The present study describes the presence and binding parameters of the A1, A2A, A2B and A3 adenosine receptors in bovinechondrocytes and fibroblast-like synoviocytes. The effect of low frequency low energy pulsed electromagnetic fields (PEMFs) on the adenosinereceptor affinity and density was studied.Methods: Saturation, competition binding experiments and Western blotting assays in the absence and in the presence of PEMFs on theadenosine receptors in bovine chondrocytes or fibroblast-like synoviocytes were performed. Thermodynamic analysis of the A2A or A3 bindingwas studied to investigate the forces driving drugereceptor coupling. In the adenylyl cyclase and proliferation assays the potency of typicalhigh-affinity A2A or A3 agonists in the absence and in the presence of PEMFs was evaluated.Results: Bovine chondrocytes and fibroblast-like synoviocytes expressed all adenosine receptors. PEMFs evoked an up-regulation of A2A andA3 receptors and thermodynamic parameters indicate that adenosine binding is enthalpy and entropy driven. In PEMF-treated cells thepotency of typical A2A or A3 agonists on cyclic AMP assays was significantly increased when compared with the untreated cells. PEMFspotentiated the effect of A2A or A3 agonists on cell proliferation in both cell types.Conclusions: PEMFs mediate an up-regulation of A2A and A3 receptors related to an increase of their functional activities in bovine chondrocytesand fibroblast-like synoviocytes. No differences are present in adenosine affinity and in the drugereceptor interactions. Our data couldbe used as a trigger to future studies addressed to PEMFs and adenosine therapeutic intervention in inflammatory joint diseases.